JP4949663B2 - Seamless belt and image forming apparatus using the same - Google Patents

Description

  The present invention relates to a seamless belt provided in an image forming apparatus such as a copy printer and the like, and an image forming apparatus using the same, and more particularly to an intermediate transfer belt suitable for full-color image formation and an image forming apparatus using the same.

  Conventionally, seamless belts have been used as members for various uses in electrophotographic apparatuses. Particularly in recent full-color electrophotographic apparatuses, an intermediate transfer belt that temporarily superimposes developed images of four colors of yellow, magenta, cyan, and black on an intermediate transfer medium and then collectively transfers them onto a transfer medium such as paper. The method is used.

  Such an intermediate transfer belt system has been used in a system that uses four color developing devices for one photoconductor, but has a drawback in that the printing speed is slow. As the high-speed printing, a four-tandem tandem system is used in which the photoreceptors are arranged for four colors and each color is continuously transferred to paper. However, in this method, there are fluctuations due to the environment of the paper, etc., and it is very difficult to match the position accuracy of overlapping each color image, causing a color misregistration image. In recent years, therefore, it has become the mainstream to adopt an intermediate transfer belt system for the 4-drum tandem system.

  For this reason, it has become necessary for the intermediate transfer belt to satisfy characteristics corresponding to requirements such as high speed and positional accuracy. In particular, for positional accuracy, it is required to suppress fluctuation due to deformation such as elongation of the belt itself due to continuous use. Further, since the intermediate transfer belt is laid out over a wide area of the apparatus and a high voltage for transfer is applied, flame retardancy is also required. Therefore, polyimide, polyamideimide resin, and the like, which are high elastic modulus and high heat resistance resins, are mainly used. Although polyimide is excellent in physical properties, it has drawbacks such as high material cost, high drying temperature of 300 ° C. or higher, and poor storage stability of the film forming solution. It is getting bigger. In that respect, polyamideimide is excellent but has high rigidity. Therefore, when it is used for a seamless belt for electrophotography, there is a problem that it is easy to cause cracking and short life due to continuous driving of the apparatus.

In patent document 1 (Unexamined-Japanese-Patent No. 2001-354854), the proposal is made to limit the amount of carbon black to be added and suppress the decrease in mechanical strength by setting the molecular weight of the polyamideimide to a specified value or more. In Patent Document 2 (Japanese Patent Laid-Open No. 2003-277522), a proposal has been made to improve the mechanical strength of polyamideimide by blending or copolymerizing polyamideimide and polyimide. In Patent Document 3 (Japanese Patent Laid-Open No. 2001-97519), there is a proposal for improving mechanical strength by reacting a compound capable of reacting with polyamideimide. Furthermore, Patent Document 4 (Japanese Patent Laid-Open No. 2003-147199) and Patent Document 5 (Japanese Patent Laid-Open No. 2003-261767) have a strength suitable for a belt by using a polyamideimide resin having a defined logarithmic viscosity. Proposed.
On the other hand, the uniformity of electrical resistance was proposed by using carbon black having specific physical properties such as Patent Document 6 (Japanese Patent Laid-Open No. 2000-338789) and Patent Document 7 (Japanese Patent Laid-Open No. 2001-47451). There is something.
However, none of these were sufficient to achieve both mechanical durability and electrical characteristics when used as an electrophotographic seamless belt such as an intermediate transfer belt.

JP 2001-354854 A JP 2003-277522 A JP 2001-97519 A JP 2003-147199 A JP 2003-261767 A JP 2000-338789 A JP 2001-47451 A

  The present invention relates to a highly durable electrophotographic seamless belt that does not cause damage such as cracks over a long period of time, particularly an intermediate transfer belt and an image forming apparatus using the intermediate transfer belt, particularly an image suitable for full-color image formation. An object is to provide a forming apparatus.

  As a result of intensive studies, the present inventors have found that when a belt is produced using a high molecular weight polyamideimide resin solution, the mechanical strength is excellent. However, when the molecular weight has a sufficient mechanical strength, the solution viscosity becomes too high, making it difficult to disperse the carbon black in the resin solution, resulting in poor dispersibility and non-uniform electrical resistance. Moreover, although the viscosity was sufficiently lowered with a solvent to prepare a coating solution, since the solid content was too low, the film thickness uniformity in the coating / drying process was deteriorated, which was not preferable. Therefore, the present inventors have found that the above-mentioned problems can be solved by forming a film with a coating solution having at least two types of polyamideimide resin solutions having different molecular weights. It came to be completed.

That is, the said subject is solved by following (1)-(11) of this invention.
(1) “Seamless belt coating solution used for electrophotography formed by a coating solution containing a polyamideimide resin solution as a main component, the coating solution containing carbon black, and the polyamideimide The resin solution is a mixture of a polyamideimide resin solution having a low molecular weight and a polyamideimide resin solution having a high molecular weight, and the polyamideimide resin solution having a high molecular weight and the polyamideimide resin solution having a low molecular weight are N A coating solution for a seamless belt for electrophotography , wherein the viscosity difference is 4 Pa · s or more and 26 Pa · s or less when methyl-2-pyrrolidone is used as a solvent and the concentration is 10 wt% solid content ”,
(2) "the small molecular weight polyamide-imide resin solution, N- methyl-2-pyrrolidone as a solvent, a resin solution comprising a resin, such as viscosity at solids 10 wt% is equal to or less than 25 Pa · s, the The polyamideimide resin solution having a large molecular weight is a resin solution comprising N-methyl-2-pyrrolidone as a solvent and a resin having a viscosity at 10 wt% of more than 25 Pa · s. The coating solution for seamless belts for electrophotography according to the item)),
(3) “Dispersion preparing step in which the coating liquid disperses carbon black in the polyamideimide resin solution having a small molecular weight , and then coating in which the dispersion and the polyamideimide resin solution having a large molecular weight are mixed. the paragraph (1) or the (2) electrophotographic seamless belt coating solution according to claim, characterized in that those produced by the methods having a liquid manufacturing process ",
(4) “A method for producing a seamless belt coating solution used for electrophotography formed by a coating solution containing a polyamideimide resin solution as a main component, in which carbon black is dispersed in a polyamideimide resin solution having a low molecular weight. A dispersion liquid preparation step, and a coating liquid preparation step of mixing the dispersion liquid and at least two types of polyamideimide resin solutions of a polyamideimide resin solution having a large molecular weight, the polyamideimide resin having a large molecular weight. The solution and the polyamideimide resin solution having a low molecular weight have a viscosity difference of 4 Pa · s or more and 26 Pa · s or less when N-methyl-2-pyrrolidone is used as a solvent and the concentration is 10 wt% solid content. And a method for producing a coating solution for a seamless belt for electrophotography ",
(5) “The polyamideimide resin solution having a low molecular weight is a resin solution made of a polyamideimide resin using N-methyl-2-pyrrolidone as a solvent and having a viscosity at a solid content of 10 wt% of 25 Pa · s or less . the large polyamideimide resin of the molecular weight is that the N- methyl-2-pyrrolidone as a solvent, wherein the viscosity of a solid content 10 wt% is a resin solution consisting of larger such resins than 25 Pa · s “Method for producing coating solution for electrophotographic seamless belt according to item (4)”,
(6) “Seamless belt used for electrophotography formed into a film by a coating solution containing a polyamide-imide resin solution as a main component, the coating solution containing carbon black and having a low molecular weight A polyamideimide resin solution prepared by mixing at least two kinds of a resin solution and a polyamideimide resin solution having a high molecular weight is used. The polyamideimide resin solution having a high molecular weight and the polyamideimide resin solution having a low molecular weight are N-methyl- A seamless belt for electrophotography characterized by having a viscosity difference of 4 Pa · s or more and 26 Pa · s or less when 2-pyrrolidone is used as a solvent and a 10 wt% solid content concentration ”,
(7) "The small molecular weight polyamide-imide resin solution, N- methyl-2-pyrrolidone as a solvent, a resin solution comprising a resin, such as viscosity at solids 10 wt% is equal to or less than 25 Pa · s, the The polyamideimide resin solution having a large molecular weight is a resin solution comprising N-methyl-2-pyrrolidone as a solvent and a resin having a viscosity at 10 wt% of more than 25 Pa · s. ) Seamless belt for electrophotography as described in the section "
(8) “The coating solution is a dispersion preparation step in which carbon black is dispersed in the polyamideimide resin solution having a small molecular weight , and then the coating solution in which the dispersion and the polyamideimide resin solution having a large molecular weight are mixed. wherein the (6) term or the (7) the electrophotographic seamless belt according to claim, characterized in that those produced by the methods having a liquid manufacturing process ",
(9) “Primary transfer is performed by sequentially superimposing a plurality of color toner developed images sequentially formed on the image carrier on the intermediate transfer belt, and the obtained primary transfer images are collectively transferred to a recording medium as a secondary. An intermediate transfer belt used in an image forming apparatus for transferring, wherein the intermediate transfer belt is the electrophotographic seamless belt according to any one of (6) to (8). "
(10) “A plurality of color toner images sequentially formed on the image carrier are sequentially superimposed on the intermediate transfer belt to perform primary transfer, and the obtained primary transfer images are collectively transferred to a recording medium as a secondary. In the image forming apparatus to be transferred, the intermediate transfer belt is the one described in item (9) above, ”
(11) In the above (10), wherein the image forming apparatus is a full-color image forming apparatus, and a plurality of latent image carriers having developing units of respective colors are arranged in series. Image forming device "

  According to the present invention, there are provided a seamless belt, an intermediate transfer belt, and an image forming apparatus using the intermediate transfer belt, which are used in an image forming apparatus having the following effects, which has improved the problems of the prior art.

According to the invention of (1), a seamless belt having a uniform electrical resistance and mechanical properties that can withstand driving in an electrophotographic apparatus is obtained.
According to the invention of (2), the carbon black to be added can be further improved in dispersibility.
According to the inventions of (3) and (4), a coating liquid for producing the seamless belt of (1) can be obtained.
According to the invention of (5), an intermediate transfer belt having the effects of the present invention can be obtained.
According to the invention of (6), an image forming apparatus having the effects of the present invention can be manufactured.
According to the invention of (7), a higher-speed full-color image forming apparatus can be provided.

In an electrophotographic apparatus, a seamless belt is used for several members, and an intermediate transfer belt is one of important members that require electrical characteristics.
In the present invention, this intermediate transfer belt will be particularly described.
The intermediate transfer belt of the present invention includes a general general-purpose resin as a constituent material containing carbon black as a filler for adjusting electric resistance. The resin is preferably selected from fluorine-based resins such as PVdF and ETFE, polyimide or polyamideimide from the viewpoint of flame retardancy.
Examples of the carbon black for adjusting the electric resistance include ketjen black, furnace black, acetylene black, thermal black, and gas black.
However, fluororesins have poor affinity with carbon black and are difficult to disperse uniformly, and problems such as resistance variation and resistance decrease due to long-term use are likely to occur.
In addition, since the tensile modulus and tensile strength are low, there is a problem that when the apparatus is left standing for a long time in a state of being stretched with a constant tension in the electrophotographic apparatus, it is deformed and cannot be stably driven.
On the other hand, polyimide can overcome the above-mentioned problems, but the stability of the solution is low because a solution in the state of polyamic acid is used. Moreover, since the temperature for curing and drying is as high as 300 ° C. or higher, the time and energy required for production are large, which is not preferable in terms of cost and environmental load. From this point, it is preferable to use polyamideimide.

Next, the polyamideimide resin will be described.
Polyamideimide is a resin having a rigid imide group and an amide group imparting flexibility in the molecular skeleton, and the polyamideimide used in the present invention may have a generally known structure. it can.
In general, as a method for synthesizing a polyamideimide resin, (a) acid chloride method: a derivative halide of a trivalent carboxylic acid having an acid anhydride group, most typically a chloride compound of the derivative and a diamine as a solvent There is known a known method for producing it by reacting in the method (for example, see Japanese Examined Patent Publication No. 42-15637). Alternatively, as another method, (b) Isocyanate method: a known method for producing by reacting a trivalent derivative containing an acid anhydride group and a carboxylic acid and an aromatic isocyanate in a solvent (for example, Japanese Examined Patent Publication No. 44-19274). Etc.) are known, and any of them can be used. Each manufacturing method will be described below.

(A) Acid chloride method As a derivative halide compound of a trivalent carboxylic acid having an acid anhydride group, for example, compounds represented by the following formulas (1) and (2) can be used.

（式中、Ｘはハロゲン元素を示す。）

(In the formula, X represents a halogen element.)

（式中、Ｘはハロゲン元素を示し、Ｙは−ＣＨ_２−、−ＣＯ−、−ＳＯ_２−または−Ｏ−を示す）

(Wherein X represents a halogen element, and Y represents —CH ₂ —, —CO—, —SO ₂ — or —O—)

  In each of the above formulas, the halogen element is preferably chloride, and specific examples of derivatives include terephthalic acid, isophthalic acid, 4, 4 ′ biphenyl dicarboxylic acid, 4, 4 ′ biphenyl ether dicarboxylic acid, 4, 4 ′ biphenyl sulfone dicarboxylic acid. Acid, 4, 4 'benzophenone dicarboxylic acid, pyromellitic acid, trimellitic acid, 3, 3', 4, 4 'benzophenone tetracarboxylic acid, 3, 3,' 4, 4 'biphenylsulfone tetracarboxylic acid, 3, Polyvalent carboxylic acids such as 3 ′, 4 and 4 ′ biphenyltetracarboxylic acid, adipic acid, sebacic acid, maleic acid, fumaric acid, dimer acid, stilbene dicarboxylic acid, 1,4 cyclohexanedicarboxylic acid, and 1,2 cyclohexanedicarboxylic acid Of acid chloride.

On the other hand, the diamine is not particularly limited, and any of aromatic diamine, aliphatic diamine, and alicyclic diamine can be used, and aromatic diamine is preferably used.
Aromatic diamines include m-phenylenediamine, p-phenylenediamine, oxydianiline, methylenediamine, hexafluoroisopropylidenediamine, diamino-m-xylylene, diamino-p-xylylene, 1,4-naphthalenediamine, 1, 5-naphthalenediamine, 2,6-naphthalenediamine, 2,7-naphthalenediamine, 2,2′-bis- (4-aminophenyl) propane, 2,2′-bis- (4-aminophenyl) hexafluoro Propane, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl ether, 3,4-diaminobiphenyl, 4,4'-diaminobenzophenone 3,4-diaminodiphenyl ether, iso Propylidenedianiline, 3,3′-diaminobenzophenone, o-tolidine, 2,4-tolylenediamine, 1,3-bis- (3-aminophenoxy) benzene, 1,4-bis- (4-aminophenoxy) ) Benzene, 1,3-bis- (4-aminophenoxy) benzene, 2,2-bis- [4- (4-aminophenoxy) phenyl] propane, bis- [4- (4-aminophenoxy) phenyl] sulfone Bis- [4- (3-aminophenoxy) phenyl] sulfone, 4,4′-bis- (4-aminophenoxy) biphenyl, 2,2′-bis- [4- (4-aminophenoxy) phenyl] Examples include xafluoropropane, 4,4′-diaminodiphenyl sulfide, and 3,3′-diaminodiphenyl sulfide.

  In order to obtain the polyamideimide (polyamideimide resin) in the present invention by the acid chloride method, the above-described trivalent carboxylic acid derivative halide and diamine having an acid anhydride group are used in the same manner as in the production of the polyimide resin. After dissolving in an organic polar solvent, it is reacted at a low temperature (0 to 30 ° C.) to obtain a polyamideimide precursor (polyamide-amic acid).

  The organic polar solvent that can be used is the same as that of the polyimide, and a formamide solvent (for example, a sulfoxide solvent such as dimethyl sulfoxide and diethyl sulfoxide, N, N-dimethylformamide, N, N-diethylformamide, etc.) , Acetamide solvents (eg, N, N-dimethylacetamide, N, N-diethylacetamide, etc.), pyrrolidone solvents (eg, N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, etc.), phenol solvents (Eg, phenol, o-, m-, or p-cresol, xylenol, halogenated phenol, catechol, etc.), ether solvents (eg, tetrahydrofuran, dioxane, dioxolane, etc.), alcohol solvents (eg, methanol, ethanol, Butanol ), Cellosolve-based solvents (e.g., butyl cellosolve, etc.), or hexamethylphosphoramide, γ- butyrolactone. These are preferably used alone or as a mixed solvent, and are not particularly limited as long as they dissolve polyamic acid. Particularly preferably used solvents are N, N-dimethylacetamide and N-methyl-2-pyrrolidone.

After the polyamide / polyamic acid solution obtained as described above is applied to a support (molding mold), conversion (imidation) from polyamic acid to polyimide is performed by treatment such as heating.
Examples of the imidization method include a method of dehydrating and ring-closing by heat treatment, and a method of chemically ring-closing using a dehydrating and ring-closing catalyst. When dehydrating and ring-closing by heat treatment, for example, the reaction temperature is 150 to 400 ° C., preferably 180 to 350 ° C., and the heat treatment time is 30 seconds to 10 hours, preferably 5 minutes to 5 hours. When a dehydration ring closure catalyst is used, the reaction temperature is 0 to 180 ° C., preferably 10 to 80 ° C., and the reaction time is several tens of minutes to several days, preferably 2 to 12 hours. Examples of the dehydration ring closure catalyst include acid anhydrides such as acetic acid, propionic acid, butyric acid, and benzoic acid.

(B) Isocyanate method As the derivative of the trivalent carboxylic acid having an acid anhydride group used in the isocyanate method, for example, a compound represented by the formula (3) or the formula (4) can be used.

（式中、Ｒは水素、炭素数１〜１０のアルキル基またはフェニル基を示す。）

(In the formula, R represents hydrogen, an alkyl group having 1 to 10 carbon atoms, or a phenyl group.)

（式中、Ｒは水素、炭素数１〜１０のアルキル基またはフェニル基を示し、Ｙは−ＣＨ_２−、−ＣＯ−、−ＳＯ_２−または−Ｏ−を示す。）

(In the formula, R represents hydrogen, an alkyl group having 1 to 10 carbon atoms, or a phenyl group, and Y represents —CH ₂ —, —CO—, —SO ₂ —, or —O—).

  Any derivative having the above general formula can be used, but the most typical example is trimellitic anhydride. These trivalent carboxylic acid derivatives having an acid anhydride group can be used alone or in combination depending on the purpose.

Next, as one aromatic polyisocyanate used for the synthesis of the polyamideimide of the present invention, for example, 4,4′-diphenylmethane diisocyanate, tolylene diisocyanate, xylylene diisocyanate, 4,4′-diphenyl ether diisocyanate, 4, 4 '-[2,2-bis (4-phenoxyphenyl) propane] diisocyanate, biphenyl-4,4'-diisocyanate, biphenyl-3,3'-diisocyanate, biphenyl-3,4'-diisocyanate, 3,3'-Dimethylbiphenyl-4,4'-diisocyanate,2,2'-dimethylbiphenyl-4,4'-diisocyanate,3,3'-diethylbiphenyl-4,4'-diisocyanate,2,2'-diethylbiphenyl-4 , 4'-diisocyanate, 3,3'-dimeth Shi biphenyl-4,4'-diisocyanate, 2,2'-dimethoxy-biphenyl-4,4'-diisocyanate, naphthalene-1,5-diisocyanate, naphthalene 2,6-diisocyanate, and the like.
These aromatic polyisocyanates can be used alone or in combination. Hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, transcyclohexane-1,4-diisocyanate, hydrogenated m-xylylene diene as necessary Aliphatic such as isocyanate and lysine diisocyanate, alicyclic isocyanate and trifunctional or higher polyisocyanate can also be used.

  After applying a solution containing a polyamidoimide precursor obtained by adjusting the above-described trivalent carboxylic acid derivative having an acid anhydride group and an aromatic polyisocyanate in an organic polar solvent, heat treatment is performed. By doing so, the conversion from the polyamideimide precursor to the polyamideimide is performed. Upon conversion to polyamideimide by this method, polyamideimide is generated without generating a carbonic acid (generally generating carbon dioxide). The following formula (5) shows an example of polyamide imidization when trimellitic anhydride and aromatic isocyanate are used.

（式中、Ａｒは芳香族基を示し、ｎは整数を示す。）
重合度としては、数平均分子量が１万〜１０万であることが好ましい。

(In the formula, Ar represents an aromatic group, and n represents an integer.)
As the degree of polymerization, the number average molecular weight is preferably 10,000 to 100,000.

The polyamideimides shown above are usually used alone, but in the present invention, it is preferable to use two types having different molecular weights selected in consideration of compatibility.
Moreover, the copolymer which has a polyimide repeating unit and a polyamideimide repeating unit may be sufficient.

In the production method as described above, the molecular weight can be adjusted by the monomer charging method, reaction temperature, reaction time, and the like.
However, since the solution viscosity becomes higher as the molecular weight increases, the production becomes increasingly difficult.
After the polymerization, it may be diluted with a solvent in order to further adjust the viscosity.

In the present invention, N-methyl-2-pyrrolidone is preferably selected as a solvent for dispersibility with carbon black, and a polyamideimide resin solution is prepared with this solvent. The prepared polyimide resin solution is prepared by adjusting the solid content and viscosity preferable for production. In the present invention, the viscosity of the resin solution when the polyamide imide resin solution is adjusted to 10 wt% solid content is used. Is a resin solution made of a resin that is 25 Pa · s or less, and a resin solution made of a resin that is more than 25 Pa · s.
Although both are not limited to those having the same composition, those having the same composition are preferred from the viewpoint of affinity.

By using a material having a viscosity per solid content of 10 wt% of 25 Pa · s or less, a liquid having excellent dispersibility of carbon black can be produced. However, sufficient mechanical strength to withstand the use of the electrophotographic apparatus cannot be obtained.
Therefore, this point is eliminated by using a material having a viscosity per solid content of 10 wt% larger than 25 Pa · s.
As for the ratio of both, the latter with a larger molecular weight is more preferable.
The present invention can be achieved by using two kinds of resins having a viscosity at a solid content of 10 wt% and a polymerization degree of the specific value.
The viscosity is determined by the solid content and the degree of polymerization, and the viscosity at a certain solid content can be used as an index of the degree of polymerization (molecular weight) of the resulting resin.
In actual production, the polymer resin solution is finally adjusted to a solid content and viscosity that are easy to handle for reasons such as facility convenience and increased yield. In the present invention, the degree of polymerization (molecular weight) of the obtained resin is defined by defining the viscosity when the resin solution thus adjusted to have any solid content and viscosity is further adjusted to 10 wt%. It is not intended to produce a coating liquid using a resin solution adjusted to a solid content of 10 wt%.

The coating solution is preferably prepared as follows.
First, a bead mill, a ball mill, a nanomizer, a paint shaker with a resin solution in which a carbon black is adjusted to an arbitrary solid content from a polyamideimide resin having a viscosity of 25 Pa · s or less at a solid content of 10 wt%. Then, the dispersion is finely dispersed using a disperser such as a jet mill.
After the dispersion is taken out, the resin solution is made of a polyamide-imide resin so that the viscosity at a solid content of 10 wt% is greater than 25 Pa · s, and the coating liquid is adjusted to a desired carbon black addition amount. And

  In the step of preparing the dispersion, the ratio of the resin and carbon black may be selected so as to be easily dispersed and diluted to an appropriate viscosity with a solvent. Moreover, you may add general purpose dispersing agents, such as surfactant.

Next, centrifugal molding, which is one of the most preferable methods, will be described as a method for producing a seamless belt using a coating liquid containing a polyamideimide precursor.
The following description is an example of belt production and is not limited to this.
Centrifugal molding is composed of a cylindrical rotating body. While this cylindrical rotating body is slowly rotated, coating and casting (coating film coating) is performed so that the coating liquid is uniform over the entire inner surface of the cylinder. Form. And the solvent in a coating film is evaporated at the temperature of about 80-150 degreeC, heating up gradually while rotating. In this process, it is preferable to efficiently circulate and remove atmospheric vapor (such as a volatilized solvent). When a self-supporting film is obtained, it is returned to room temperature, transferred to a heating furnace (firing furnace) capable of high-temperature treatment, heated in steps, and finally subjected to heat treatment at about 200 ° C. to 270 ° C. . After the heating is completed, the film is slowly cooled to peel the film from the mold. A seamless belt is thus formed. In addition, it is preferable to previously form a mold release agent or a mold release layer on the mold so that the mold can be easily peeled off.

Next, a seamless belt used in a belt constituting unit provided in the image forming apparatus according to the present invention will be described in detail below with reference to a schematic diagram of a main part. The schematic diagram is an example, and the present invention is not limited to this.
The schematic diagram of FIG. 1 shows a schematic configuration of a main part of an image forming apparatus equipped with a belt member and the like.
The intermediate transfer unit (500) including the belt member shown in FIG. 1 includes an intermediate transfer belt (501) that is an intermediate transfer member stretched around a plurality of rollers. Around the intermediate transfer belt (501), there are a secondary transfer bias roller (605) as a secondary transfer charge applying means of the secondary transfer unit (600), and a belt cleaning blade (504) as an intermediate transfer body cleaning means. A lubricant application brush (505), which is a lubricant application member of the lubricant application means, is disposed so as to face each other.

  Further, position detection marks (not shown) are provided on the outer peripheral surface or inner peripheral surface of the intermediate transfer belt (501). However, on the outer peripheral surface side of the intermediate transfer belt (501), it is necessary to devise a position detection mark that avoids the passing area of the belt cleaning blade (504), which may be difficult to arrange. In this case, a position detection mark may be provided on the inner peripheral surface side of the intermediate transfer belt (501). The optical sensor (514) serving as a mark detection sensor is provided at a position between the primary transfer bias roller (507) and the belt driving roller (508) on which the intermediate transfer belt (501) is stretched.

  The intermediate transfer belt (501) includes a primary transfer bias roller (507), a belt driving roller (508), a belt tension roller (509), a secondary transfer counter roller (510), which are primary transfer charge applying means, and a cleaning device. It is stretched between the counter roller (511) and the feedback current detection roller (512). Each roller is made of a conductive material, and each roller other than the primary transfer bias roller (507) is grounded. The primary transfer bias roller (507) is controlled by a primary transfer power source (801) controlled by a constant current or a constant voltage so that the current or voltage is controlled to a predetermined magnitude according to the number of superimposed toner images. A bias is applied.

The intermediate transfer belt (501) is driven in the direction of the arrow by a belt drive roller (508) that is driven to rotate in the direction of the arrow by a drive motor (not shown).
The intermediate transfer belt (501) as the belt member is usually a semiconductor or an insulator and has a single-layer or multi-layer structure, but in the present invention, a seamless belt is preferably used, thereby improving durability. In addition, excellent image formation can be realized. In addition, the intermediate transfer belt is set to be larger than the maximum sheet passing size in order to superimpose the toner images formed on the photosensitive drum (200).

  A secondary transfer bias roller (605), which is a secondary transfer means, is in contact with / separating means, which will be described later, with respect to the belt outer peripheral surface of a portion of the intermediate transfer belt (501) stretched around the secondary transfer counter roller (510). It is comprised so that contact / separation is possible by the contact / separation mechanism. The secondary transfer bias roller (605) sandwiches the transfer paper (P) as a recording medium between the secondary transfer counter roller (510) and the intermediate transfer belt (501) stretched between the secondary transfer counter roller (510). A transfer bias having a predetermined current is applied by a secondary transfer power source (802) that is arranged and controlled at a constant current.

  The registration roller (610) is a transfer sheet as a transfer material at a predetermined timing between the secondary transfer bias roller (605) and the intermediate transfer belt (501) stretched around the secondary transfer counter roller (510). Send (P). Further, a cleaning blade (608) as a cleaning unit is in contact with the secondary transfer bias roller (605). The cleaning blade (608) removes and removes adhering material adhering to the surface of the secondary transfer bias roller (605).

  In the color copying machine having such a configuration, when the image forming cycle is started, the photosensitive drum (200) is rotated in a counterclockwise direction indicated by an arrow by a driving motor (not shown), and the photosensitive drum (200) is rotated on the photosensitive drum (200). In addition, Bk (black) toner image formation, C (cyan) toner image formation, M (magenta) toner image formation, and Y (yellow) toner image formation are performed. The intermediate transfer belt (501) is rotated clockwise by the belt driving roller (508) as indicated by an arrow. As the intermediate transfer belt (501) rotates, the primary transfer of the Bk toner image, the C toner image, the M toner image, and the Y toner image is performed by the transfer bias by the voltage applied to the primary transfer bias roller (507). Finally, toner images are formed on the intermediate transfer belt (501) in the order of Bk, C, M, and Y.

For example, the Bk toner image formation is performed as follows.
In FIG. 1, a charging charger (203) uniformly charges the surface of the photosensitive drum (200) to a predetermined potential with a negative charge by corona discharge. The timing is determined based on the belt mark detection signal, and raster exposure with laser light is performed based on the Bk color image signal by a writing optical unit (not shown). When this raster image is exposed, the charge proportional to the exposure light amount disappears in the exposed portion of the surface of the photosensitive drum (200) that is initially charged uniformly, and a Bk electrostatic latent image is formed. When the negatively charged Bk toner on the developing roller of the Bk developing device (231K) comes into contact with this Bk electrostatic latent image, the toner adheres to the portion where the charge of the photosensitive drum (200) remains. In other words, toner is attracted to a portion having no charge, that is, an exposed portion, and a Bk toner image similar to the electrostatic latent image is formed.

  The Bk toner image formed on the photosensitive drum (200) in this way is primary on the belt outer peripheral surface of the intermediate transfer belt (501) rotating at a constant speed while being in contact with the photosensitive drum (200). Transcribed. Some untransferred residual toner remaining on the surface of the photoreceptor drum (200) after the primary transfer is cleaned by the photoreceptor cleaning device (201) in preparation for reuse of the photoreceptor drum (200). Is done. On the photosensitive drum (200) side, the process proceeds to the Y image forming process after the Bk image forming process, and reading of Y image data by a color scanner starts at a predetermined timing. A Y electrostatic latent image is formed on the surface of the body drum (200).

  Then, after the rear end portion of the previous Bk electrostatic latent image passes and before the front end portion of the Y electrostatic latent image arrives, the revolver developing unit (230) is rotated, and the Y developing machine ( 231Y) is set at the development position, and the Y electrostatic latent image is developed with Y toner. Thereafter, the development of the Y electrostatic latent image area is continued, but when the rear end of the Y electrostatic latent image passes, the revolver developing unit is rotated in the same manner as in the previous Bk developing machine (231K). Then, the next C developing machine (231C) is moved to the developing position. This is also completed before the leading edge of the next C electrostatic latent image reaches the developing position. Note that the C and M image forming steps are the same as the Bk and Y steps described above because the color image data reading, electrostatic latent image forming, and developing operations are the same as those described above.

The Bk, Y, C, and M toner images sequentially formed on the photosensitive drum (200) in this manner are sequentially aligned on the same surface on the intermediate transfer belt (501) and primarily transferred. As a result, a toner image having a maximum of four colors superimposed on the intermediate transfer belt (501) is formed. On the other hand, at the time when the image forming operation is started, the transfer paper P is fed from a paper feed unit such as a transfer paper cassette or a manual feed tray, and is waiting at the nip of the registration roller (610).
Then, on the intermediate transfer belt (501), the intermediate transfer belt (501) stretched around the secondary transfer counter roller (510) and the secondary transfer bias roller (605) form a nip. When the leading edge of the toner image approaches, the registration roller (610) is driven so that the leading edge of the transfer paper (P) coincides with the leading edge of the toner image, and is transferred along the transfer paper guide plate (601). The paper (P) is conveyed and registration of the transfer paper (P) and the toner image is performed.

  In this way, when the transfer paper (P) passes through the secondary transfer portion, the intermediate transfer belt (501) is transferred by the transfer bias generated by the voltage applied to the secondary transfer bias roller (605) by the secondary transfer power source (802). ) The four-color superimposed toner image on the top is transferred onto the transfer paper (P) at once (secondary transfer). This transfer paper (P) is conveyed along the transfer paper guide plate (601) and passes through a portion facing the transfer paper neutralization charger (606) comprising a static elimination needle disposed downstream of the secondary transfer portion. After being neutralized by this, the belt is conveyed toward the fixing device (270) by the belt conveying device (210) which is a belt component (see FIG. 1). Then, after the toner image is melted and fixed at the nip portion of the fixing rollers (271) and (272) of the fixing device (270), the transfer paper (P) is sent out of the apparatus main body by a discharge roller (not shown). Stacked face up on a copy tray (not shown). Note that the fixing device (270) may be configured to include a belt component if necessary.

  On the other hand, the surface of the photosensitive drum (200) after the belt transfer is cleaned by the photosensitive member cleaning device (201) and is uniformly discharged by the discharging lamp (202). The residual toner remaining on the outer peripheral surface of the intermediate transfer belt (501) after the toner image is secondarily transferred to the transfer paper (P) is cleaned by the belt cleaning blade (504). The belt cleaning blade (504) is configured to contact and separate at a predetermined timing with respect to the belt outer peripheral surface of the intermediate transfer belt (501) by a cleaning member separating and contacting mechanism (not shown).

  A toner seal member (503) that contacts and separates from the belt outer peripheral surface of the intermediate transfer belt (501) is provided on the upstream side of the belt cleaning blade (504) in the moving direction of the intermediate transfer belt (501). Yes. The toner seal member (503) receives the falling toner dropped from the belt cleaning blade (504) during cleaning of the residual toner, and the falling toner is scattered on the transfer path of the transfer paper (P). It is preventing. The toner seal member (503) is brought into contact with and separated from the belt outer peripheral surface of the intermediate transfer belt (501) together with the belt cleaning blade (504) by the cleaning member separating and contacting mechanism.

  The lubricant (506) scraped by the lubricant application brush (505) is applied to the belt outer peripheral surface of the intermediate transfer belt (501) from which the residual toner has been removed in this way. The lubricant (506) is made of, for example, a solid body such as zinc stearate, and is disposed so as to come into contact with the lubricant application brush (505). Further, residual charges remaining on the outer peripheral surface of the intermediate transfer belt (501) are removed by a neutralizing bias applied by a belt neutralizing brush (not shown) in contact with the outer peripheral surface of the intermediate transfer belt (501). Here, the lubricant application brush (505) and the belt neutralizing brush are brought into and out of contact with the outer peripheral surface of the intermediate transfer belt (501) at a predetermined timing by a contact / separation mechanism (not shown). It has become.

  Here, at the time of repeat copy, the operation of the color scanner and the image formation on the photosensitive drum (200) are performed at a predetermined timing following the image formation process for the fourth color (M) of the first sheet. The process proceeds to the image forming process for the first color (Bk). The intermediate transfer belt (501) has two sheets in the area cleaned by the belt cleaning blade (504) on the outer peripheral surface of the belt following the batch transfer process of the first four-color superimposed toner image to the transfer paper. The Bk toner image of the eye is primarily transferred. After that, the operation is the same as the first sheet. The above is a copy mode for obtaining a four-color full-color copy. In the three-color copy mode and the two-color copy mode, the same operation as described above is performed for the designated color and number of times. In the case of the single color copy mode, only the developing device of the predetermined color of the revolver developing unit (230) is set in the developing operation state until the predetermined number of sheets is completed, and the belt cleaning blade (504) is moved to the intermediate transfer belt (501). The copy operation is performed with the touch panel kept in contact.

In the above-described embodiment, the copying machine including only one photosensitive drum 1 has been described. However, the present invention may be configured such that, for example, a plurality of photosensitive drums as illustrated in FIG. 2 are arranged in parallel along one intermediate transfer belt. The present invention can also be applied to the image forming apparatus.
FIG. 2 shows a four-drum type digital color printer having four photosensitive drums (21BK, 21Y, 21M, 21C) for forming toner images of four different colors (black, yellow, magenta, cyan). An example of the configuration is shown.

  In FIG. 2, the printer main body (10) includes an image writing unit (12), an image forming unit (13), and a paper feeding unit (14) for performing color image formation by electrophotography. Based on the image signal, the image processing unit converts the image into black (BK), magenta (M), yellow (Y), and cyan (C) color signals for image formation, and the image writing unit (12). Send to. The image writing unit (12) is a laser scanning optical system including, for example, a laser light source, a deflector such as a rotary polygon mirror, a scanning imaging optical system, and a mirror group. Image writing corresponding to each color signal is performed on an image carrier (photoreceptor) (21BK, 21M, 21Y, 21C) provided for each color of the image forming unit (13).

  The image forming unit (13) includes photosensitive members (21BK, 21M, 21Y, and 21C) that are image carriers for black (BK), magenta (M), yellow (Y), and cyan (C). I have. As each photoconductor for each color, an OPC photoconductor is usually used. Around each photosensitive member (21BK, 21M, 21Y, 21C), there are a charging device, a laser beam exposure unit from the writing unit (12), and a developing device (20BK) for each color of black, magenta, yellow, and cyan. , 20M, 20Y, 20C), a primary transfer bias roller (23BK, 23M, 23Y, 23C) as a primary transfer unit, a cleaning device (not shown), a photoconductor neutralizing device (not shown), and the like. . The developing device (20BK, 20M, 20Y, 20C) uses a two-component magnetic brush developing system. The intermediate transfer belt (22), which is a belt component, is interposed between each photoconductor (21BK, 21M, 21Y, 21C) and each primary transfer bias roller (23BK, 23M, 23Y, 23C). The toner images of the respective colors formed on the photoconductor are sequentially superimposed and transferred.

  On the other hand, the transfer paper (P) is fed from the paper feeding section (14) and then carried on the transfer conveyance belt (50), which is a belt constituting section, via the registration rollers (16). When the intermediate transfer belt (22) and the transfer conveying belt (50) come into contact with each other, the toner image transferred onto the intermediate transfer belt (22) is transferred to a secondary transfer bias roller (60) as a secondary transfer unit. ) For secondary transfer (collective transfer). Thereby, a color image is formed on the transfer paper (P). The transfer paper (P) on which the color image is formed is conveyed to the fixing device (15) by the transfer conveying belt (50). After the image transferred by the fixing device (15) is fixed, the transfer paper (P) is removed from the printer main body. To be discharged.

  The residual toner that is not transferred during the secondary transfer and remains on the intermediate transfer belt (22) is removed from the intermediate transfer belt (22) by the belt cleaning device (25). A lubricant application device (not shown) is disposed on the downstream side of the belt cleaning device (25). This lubricant application device includes a solid lubricant and a conductive brush that rubs the intermediate transfer belt (22) to apply the solid lubricant. The conductive brush is always in contact with the intermediate transfer belt (22) and applies a solid lubricant to the intermediate transfer belt (22). The solid lubricant has an effect of improving the cleaning property of the intermediate transfer belt (22), preventing the occurrence of filming and improving the durability.

  EXAMPLES Hereinafter, the present invention will be described more specifically based on examples. However, the present invention is not limited by these examples, and these examples are appropriately modified without departing from the gist of the present invention. Is also within the scope of the present invention.

The characteristics evaluated in the following examples are evaluated by the following methods.
<Viscosity>
Measured with rotational viscometer Rheostress RS600 (Eihiro Seiki).
Use φ35mm / 1 ° cone sensor.
The value after 1 minute was set at 25 ° C./0.5 rpm.
<MIT weather resistance test>
Measures the number of bends until breakage with MIT weather resistance tester (Toyo Seiki).
It is preferable that the sample width is 15 mm, the bending angle is 135 degrees, the bending speed is 175 cpm, the load is 1 kg, and the number of bendings exceeds 1000.
<Electrical resistance measurement>
Measured with Hi-Lester (Mitsubishi Chemical).
Uses URS probe.
The volume resistance at the time of application of 100 V / 10 seconds was measured at 10 points, and the difference between the logarithmic value of the maximum value and the logarithm value of the minimum value was obtained as “volume resistance variation”. This value is preferably within 0.5 or less.
<Evaluation in electrophotographic apparatus>
It was mounted on the full-color electrophotographic apparatus of FIG. 2 and image evaluation was performed.
In addition, durability evaluation was performed by continuous output of 10,000 sheets.

(Example)
[Preparation of coating solution]
After reacting 1 mol of trimellitic anhydride and 1 mol of diphenylmethane diisocyanate in N-methyl-2-pyrrolidone at 120 ° C. for X hours, the mixture was further heated to 180 ° C. for 3 hours, cooled and reacted. Was stopped, and the resin solution was diluted with N-methyl-2-pyrrolidone to prepare a resin solution appropriately diluted to a viscosity that is easy to take out.
A, B, C, and D having different molecular weights were prepared by shaking reaction time X.
Table 1 shows the viscosity and solid content of each of the resin solutions A, B, C, and D.
Moreover, the viscosity at the time of diluting each resin solution to 10 wt% of solid content was described simultaneously.

Example 1
A mixture of resin solution A 10 wt%, carbon black (SpecailBlack 4; manufactured by Degussa) 10 wt% and N-methyl-2-pyrrolidone 80 wt% is put into a bead mill disperser and dispersed for a predetermined time, and then the beads and liquid are separated. Was taken out.
300 parts by weight of the resin solution C was added to 100 parts by weight of the dispersion, mixed and defoamed with a triaxial planetary kneader with a decompression function to prepare a coating liquid L.

(Example 2)
A coating liquid M was prepared in the same manner as in Example 1 except that B was used instead of the resin solution A in Example 1.

(Example 3)
A coating liquid N was prepared in the same manner as in Example 1 except that 400 parts by weight of the resin solution D was used instead of 300 parts by weight of the resin solution C.

(Comparative Example 1)
A coating solution O was prepared in the same manner as in Example 1 except that the resin solution C was 200 parts by weight instead of the resin solution C 300 parts by weight.

Example 4
A coating solution P was prepared in the same manner as in Example 1 except that the resin solution B was 250 parts by weight instead of the resin solution C 300 parts by weight.

(Example 5)
A coating solution Q was prepared in the same manner as in Example 1, except that the resin solution C was used instead of the resin solution A, and 400 parts by weight of the resin solution D was used instead of 300 parts by weight of the resin solution C.

(Comparative Example 2)
A coating solution R was prepared in the same manner as in Example 1 except that the resin solution D was used instead of the resin solution A and the resin solution C was 400 parts by weight instead of 300 parts by weight.

[Production of seamless belt]
Next, a magnetic metal cylinder having an inner diameter of 100 mm and a length of 300 mm and having a mirror finish on the inner surface is used as a mold, and the coating liquid is uniformly applied to the inner surface of the cylinder while rotating the cylinder at 50 rpm (times / minute). The solution was applied by casting. When the predetermined amount was completely poured and the coating film was evenly spread, the number of revolutions was increased to 100 rpm, the hot air circulating dryer was introduced, and the temperature was gradually raised to 110 ° C. and heated for 60 minutes. The temperature was further raised and heated at 250 ° C. for 40 minutes, and the rotation was stopped and gradually cooled and taken out. The formed coating film was peeled off from the inner surface of the cylinder to obtain each seamless belt having a film thickness of 85 μm.

  Table 2 shows the results of the MIT weather resistance test, electrical resistance, and image evaluation in the image forming apparatus shown in FIG.

  As described above, by using the seamless belt of the present invention, it is possible to obtain a full-color electrophotographic apparatus having sufficient mechanical strength in the electrophotographic apparatus, uniform electrical resistance, and capable of providing a high-quality image.

FIG. 2 is a schematic view of a main part for explaining a seamless belt used for a belt member of an image forming apparatus according to the present invention and an image forming apparatus using the same. FIG. 2 is a schematic diagram of a main part illustrating a configuration example of an image forming apparatus in which a plurality of photosensitive drums are arranged in parallel along one intermediate transfer belt provided as a belt member of the image forming apparatus according to the present invention.

Explanation of symbols

(Figure 1)
P Transfer paper 70 Static elimination roller 80 Ground roller 200 Photosensitive drum 201 Photoconductor cleaning device 202 Static elimination lamp 203 Charging charger 204 Potential sensor 205 Toner image density sensor 210 Belt conveyor 230 Revolver developing unit 231Y Y developing machine 231K Bk developing machine 231C C Developer 231M M Developer 270 Fixing device 271, 272 Fixing roller 500 Intermediate transfer unit 501 Intermediate transfer belt 503 Toner seal member 504 Belt cleaning blade 505 Lubricant application brush 506 Lubricant 507 Primary transfer bias roller 508 Belt drive roller 509 Belt Tension controller 510 Secondary transfer counter roller 511 Cleaning counter roller 512 Feedback current detection roller 513 Toner image 514 Optical sensor 6 00 Secondary transfer unit 601 Transfer paper guide plate 605 Secondary transfer bias roller 606 Transfer paper neutralization charger 608 Cleaning blade 610 Registration roller 801 Primary transfer power source 802 Secondary transfer power source (FIG. 2)
P Transfer paper 10 Printer body 12 Image writing unit 13 Image forming unit 14 Paper feeding unit 15 Fixing device 16 Registration rollers 20BK, 20M, 20Y, 20C Developing devices 21BK, 21M, 21Y, 21C Photoconductor 22 Intermediate transfer belts 23BK, 23M , 23Y, 23C Primary transfer bias roller 25 Belt cleaning device 50 Transfer conveyance belt 60 Secondary transfer bias roller

Claims (2)

A method for producing a seamless belt coating solution used for electrophotography formed by a coating solution containing a polyamideimide resin solution as a main component, wherein the dispersion is made by dispersing carbon black in a polyamideimide resin solution having a small molecular weight. And a coating liquid preparation step of mixing the dispersion and at least two types of polyamideimide resin solutions of a polyamideimide resin solution having a large molecular weight, the polyamideimide resin solution having a large molecular weight and the molecular weight The small polyamidoimide resin solution has a viscosity difference of 4 Pa · s or more and 26 Pa · s or less when N-methyl-2-pyrrolidone is used as a solvent and the concentration is 10 wt% solid content. Of a coating solution for seamless belts. The polyamideimide resin solution having a low molecular weight is a resin solution made of a polyamideimide resin using N-methyl-2-pyrrolidone as a solvent and having a viscosity at a solid content of 10 wt% of 25 Pa · s or less. large polyamideimide resin, N- methyl-2-pyrrolidone as a solvent, according to claim 1 having a viscosity at solids 10 wt% is characterized in that it is a resin solution comprising a resin, such as greater than 25 Pa · s Of producing a coating solution for seamless belt for electrophotography.

Images